1. Field
This disclosure relates to a negative electrode for an energy storage device and an energy storage device including same.
2. Description of the Related Technology
An energy storage device based on electrochemical reaction includes two electrodes, an electrolyte that transfers ions, and a separator.
The electrochemical reaction of the energy storage device is mostly a surface reaction occurring on the surface of an electrode, and a non-uniform reaction. The reaction may be categorized as a mass transfer reaction where chemical species dissociated from the electrolyte are transferred to the surface of an electrode, a non-faradaic reaction, which is an adsorption/desorption reaction where the transferred chemical species form a layer called as an electric double layer on the surface of an electrode, or a faradaic reaction, which is an electron transfer reaction where electrons are directly received and oxidized (or reduced). Among the energy storages using the former reaction is a super capacitor (or electric bilayer capacitor). As for the energy storages using the latter reaction, there is lithium rechargeable battery.
To overcome the capacitance limit of existing super capacitors, a hybrid capacitor using a lithium metal oxide which is usually used as a positive active material of a lithium rechargeable battery for a positive electrode of a super capacitor is being developed, and also researchers are studying to improve the output characteristics of a lithium rechargeable battery by adopting activated carbon, which is a material used for a positive electrode of a super capacitor, to an electrode of a positive active material. Examples of such research include Japanese Patent Laid-Open Publication Nos. 2003-077458 and 2001-351688. The research for increasing the capacitance of an energy storage device continues.